1. Field of the Invention
The present invention relates to a method for measuring the strength of a honeycomb structure provided with a hole into which, for example, a sensor is inserted.
2. Description of the Related Art
To prevent environmental pollution and improve the environment, a catalyst converter is used for the treatment of an exhaust gas from a car. This catalyst converter converts harmful substances (nitrogen oxide, carbon monoxide, etc.) included in the exhaust gas into components which can be discharged to the environment in accordance with law's provisions. When the exhaust gas passes through the catalyst converter, the harmful substances included in the gas are decreased.
However, in a case where it is confirmed whether or not the harmful substances have actually been decreased, it is difficult to directly measure the concentration of the harmful substances in the exhaust gas by use of a sensor.
To solve the problem, the function of the catalyst converter is monitored instead. When the catalyst converter functions, the harmful substances must be decreased. To monitor the function of the catalyst converter, there is employed means for arranging oxygen sensors, for example, back and forth of the catalyst converter, respectively, and measuring the content of oxygen in the exhaust gas by use of these sensors to speculate the accumulation capacity of a catalyst and the progress of an aging process. Alternatively, there is employed means for arranging heat sensors back and forth of the catalyst converter, respectively, and measuring the temperature change of the exhaust gas by use of these sensors to speculate whether or not the catalyst converter works (e.g., see JP-T-2004-526564).
When the above sensors are inserted into holes formed in a honeycomb structure similar to a carrier of the catalyst converter of the catalyst converter and installed together with the honeycomb structure in an exhaust system of the car, the exposure of the sensors to oil, fuel, condensate water and the like encountered in the exhaust system can be prevented, and the stability of the sensors for a long period can be secured. Moreover, heat is usually taken by vaporization of the condensate water to disturb the early heating of the sensors. However, when the sensors are disposed in the honeycomb structure, rapid heating by a sensor heater at an early stage can be performed, and λ-control at the early stage immediately after starting an engine is realized to obtain an emission decreasing effect. In addition, restriction on a space is eased.
It is to be noted that as a prior document suggested to solve the same theme as that of the present invention described later or a similar theme, for example, JP-T-2004-526564 can be exemplified.
Additionally, even in the honeycomb structure provided with the holes into which the sensors are inserted, a constant strength is demanded in the same manner as in a filter or the catalyst carrier. When the honeycomb structure is broken, a sensor function might be lost, and a detection accuracy might lower.
However, when the strength of the honeycomb structure provided with the holes is measured by an isostatic breakdown strength test, there are confronted problems that hole edge portions are cracked by urethane wrapping the honeycomb structure therein or urethane is broken and that the strength of the honeycomb structure cannot be measured.